Re: IPv4/IPv6 router
On Thu, 2005-01-06 at 11:45 +0100, Frederic Beck wrote:
>
> There is still a point that isn't clear for me : should i advertise my
> LAN prefix on the rest of the network. Because, if i don't advertise
> in any way this new prefixe how will the routing protocols be able to
> find my new_lan ?
It is your IPv6 provider who will route traffic to your subnet through
the address it gave you for your edge router. Same as IPv4 in fact. So
the router just needs to know where the subnet is and where the rest of
the world is.
Some more precisions about how the prefixes work : if you want to route
traffic between an IPv6 LAN and the rest of the world, then you need to
have a prefix so you can assign a subnet to your LAN. For that reason,
all good IPv6 providers propose /48 prefixes for your internal uses. Les
say that you got 3ffe:0b80:17e2:: /48. If you just want a single subnet,
substitute /64 for the /48 and you have the prefix that radvd will
advertise. But you could also cut your /48 in multiple /64 subnets by
using the last 16 bits for subnetting. For example you could have
3ffe:0b80:17e2:1: /64, 3ffe:0b80:17e2:2: /64, 3ffe:0b80:17e2:3: /64 and
so on : 16 bits give you up to 65536 /64 subnets (with 2^64 hosts
each...).
> and if yes isn't there a specific option i should set on the RA so
> that the hosts do not renumber ?
No need for that : with stateless autoconfiguration you can let the
router assign addresses that are based on the Ethernet adapter's MAC
address, so they won't change much for a given host. There are other
ways, but this one is very straightforward.
Say you have a router that advertises your 48 bit prefix, here is how
the LAN host ends up with a 128 bit address. The last 64 bits of an IPv6
address are the interface identifier that is unique to the prefix.
RFC2464 states that the interface identifier is based on the EUI-64
identifier. The IEEE EUI-64 address represents a new standard for
network interface addressing. It supersedes the MAC addressing, also
known as IEEE 802. The company ID is still 24-bits in length, but the
extension ID is 40 bits instead of only 24 in the MAC address, creating
a much larger address space for a network adapter manufacturer. So since
the Ethernet adapter you most probably use on your computer use is
certainly identified by a good old 48 bit MAC address, we'll need to map
it to a 64 bit IEEE-64. And that's where the magic ingredient comes in :
just add some padding. RFC2464 says “The fourth and fifth octets of the
EUI are set to the fixed value FFFE hexadecimal” .
I cut and pasted the above from a piece I wrote a long while ago :
http://www.ruwenzori.net/ipv6/Jims_LAN_IPv6_global_connectivity_howto.html. It may be quite dated by now, but I guess the basics are still valid.
That makes me think I definitely need to update my IPv6 knowledge...
> in fact i have the following architecture :
>
> network ---- my_router ---- my_lan
> |
> |
> DHCP
>
> the hosts behind the router in my new LAN were before directly connected
> to the network and the DHCP configures them. If is simply enable the
> IPv4 forwarding and set the corresponding rules in my netfilter conf,
> will the hosts behave normally, or do i need to configure them in static
> mode with my_router as GW ? (All hosts/servers are in the same IPv4
> network, 152.81.x.x).
Install dhcp-relay on the router. You need a subnet for the internal
LAN, but apart from that it is quite straightforward.
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